thank you very much for this resource! i'm still pretty new to renpy, so it's been a lifesaver.
for any other newbies wondering, i was able to figure out how to make oversized images (ie, for panning cgs) scrollable/draggable when viewed close-up.
just nudge the imagebutton stuff at the bottom of both.rpy into a viewport, and customize it to your liking. you'll probably want to set a custom image for the thumbnail preview, but you can find out how to do that in the comments as of this writing.
also, if you want to hide the names of any locked CGs, replace the following line from gallery.rpy:
text gallery_items[i].name
with if/else statements appropriately (example attached).